A UN spokesman said on Tuesday that the United Nations still lacks the agreement for its chemical weapons investigation mission to do its work in Syria.

To date, the UN does not have the agreement it needs for the UN fact-finding mission on the alleged use of chemical weapons in Syria, which is ready to deploy quickly to enter the country and do its on-site work, said UN spokesman Martin Nesirky here at a daily news briefing.

"The Secretary-General has concluded that the mission should also investigate the facts related to the reported incident on 23 December 2012 in Homs, not only the incident in Khan al-Assal," Nesirky said, stressing that UN Secretary-General Ban Ki-moon cannot accept engaging in a partial investigation.

Nesirky also emphasized the need for on-site investigations and reaffirming the professionalism and integrity of the team, and characterized the Syria crisis as "an extremely bloody conflict which needs to end soon through a negotiated solution."

Speaking at a press conference at UN headquarters in New York on Tuesday, Bashar Ja'afari, the Syrian permanent representative to the United Nations, wanted the UN to fulfill the request of Syrian government to "initiate an independent, genuine, technical investigation in Khan al-Assal," a village on the outskirts of Aleppo.

"We believe that the best way to reach a credible outcome through this mission can only be achieved through deploying without any delay the mission on the reported incident in Khan al- Assal," said al-Jafaari.

"The Syrian government did not close the doors of the United Nations and the investigative mission to look into any other allegations, but the principle of respecting international law requires a strict respect for the sovereignty of member states," al-Jafaari said. "We're still awaiting the receipt of any other credible information about other allegations."

Nesirky expressed welcome for the Syrian government's efforts to expedite the deployment of the UN Mission to investigate the allegations of the use of chemical weapons in Khan al-Assal and Syria's confirmation of its support and cooperation in respect of that initial deployment.

However, he noted that the Secretary-General is duty bound to take seriously all allegations made by member states and would look into all requests in the order that they were received.

The Syrian government last month accused the rebels in northern Syria of firing a chemical rocket at the town of Khan al-Asal that killed more than 26 people. The rebels denied accusations and turned the finger toward the government's forces.